Joseph M. Rudys

Genesis: A 5-MA Programmable Pulsed-Power Driver for Isentropic Compression Experiments

Enabling technologies are being developed at Sandia National Laboratories to improve the performance and flexibility of compact pulsed power drivers for magnetically driven dynamic materials properties research. We have designed a modular system capable of precision current pulse shaping through the selective triggering of pulse forming components into a disk transmission line feeding a strip line load. The system is comprised of two hundred and forty 200 kV, 60 kA modules in a low inductance configuration capable of producing 250–350 kbar of magnetic pressure in a 1.75 nH, 20 mm wide strip line load. The system, called Genesis, measures approximately 5 meters in diameter and is capable of producing shaped currents greater than 5 MA. This performance is enabled through the use of a serviceable solid dielectric insulator system which minimizes the system inductance and reduces the stored energy and operating voltage requirements. Genesis can be programmed by the user to generate precision pulse shapes with rise times of 220–500 ns, allowing characterization of a range of materials from tungsten to polypropylene. This paper provides an overview of the Genesis design including the use of genetic optimization to shape currents through selective module triggering.

Genesis: A 5 MA programmable pulsed power driver for Isentropic Compression Experiments

Enabling technologies are being developed at Sandia National Laboratories to improve the performance and flexibility of compact pulsed-power drivers for magnetically driven dynamic materials properties research. We have designed a modular system that is capable of precision current pulse shaping through the selective triggering of pulse-forming components into a disk transmission line feeding a strip line load. The system is composed of 240 200-kV 60-kA modules in a low-inductance configuration that is capable of producing 250-350 kbar of magnetic pressure in a 1.75-nH 20-mm-wide strip line load. The system, called Genesis , measures approximately 5 m in diameter and is capable of producing shaped currents that are greater than 5 MA. This performance is enabled through the use of a serviceable solid-dielectric insulator system which minimizes the system inductance and reduces the stored energy and operating voltage requirements. Genesis can be programmed by the user to generate precision pulse shapes with rise times of 220-500 ns, allowing characterization of a range of materials from tungsten to polypropylene. This paper provides an overview of the Genesis design, including the use of genetic optimization to shape currents through selective module triggering.

Status of genesis a 5 MA programmable pulsed power driver

Genesis is a compact pulsed power platform designed by Sandia National Laboratories to generate precision shaped multi-MA current waves with a rise time of 200–500 ns. In this system, two hundred and forty, 200 kV, 80 kA modules are selectively triggered to produce 280 kbar of magnetic pressure (>500 kbar pressure in high Z materials) in a stripline load for dynamic materials properties research. This new capability incorporates the use of solid dielectrics to reduce system inductance and size, programmable current shaping, and gas switches that must perform over a large range of operating conditions. Research has continued on this technology base with a focus on demonstrating the integrated performance of key concepts into a Genesis-like prototype called Protogen. Protogen measures approximately 1.4 m by 1.4 m and is designed to hold twelve Genesis modules. A fixed inductance load will allow rep-rate operation for component reliability and system lifetime experiments at the extreme electric field operating conditions expected in Genesis.

Status of Genesis a 5-MA Programmable Pulsed Power Driver

Genesis is a compact pulsed power platform designed by Sandia National Laboratories to generate precision shaped multi-MA current waves with a rise time of 200-500 ns. In this system, two hundred and forty, 200 kV, 80 kA modules are selectively triggered to produce 280 kbar of magnetic pressure (>;500 kbar pressure in high Z materials) in a stripline load for dynamic materials properties research. This new capability incorporates the use of solid dielectrics to reduce system inductance and size, programmable current shaping, and gas switches that must perform over a large range of operating conditions. Research has continued on this technology base with a focus on demonstrating the integrated performance of key concepts into a Genesis-like prototype called Protogen. Protogen measures approximately 1.4 m by 1.4 m and is designed to hold 12 Genesis modules. A fixed inductance load will allow rep-rate operation for component reliability and system lifetime experiments at the extreme electric field operating conditions expected in Genesis.

Impact of time-varying loads on the programmable pulsed power driver called genesis

The success of dynamic materials properties research at Sandia National Laboratories has led to research into ultra-low impedance, compact pulsed power systems capable of multi-MA shaped current pulses with rise times ranging from 220–500 ns. The Genesis design consists of two hundred and forty 200 kV, 80 kA modules connected in parallel to a solid dielectric disk transmission line and is capable of producing 280 kbar of magnetic pressure (>500 kbar pressure in high Z materials) in a 1.75 nH, 20 mm wide stripline load. Stripline loads operating under these conditions expand during the experiment resulting in a time-varying load that can impact the performance and lifetime of the system. This paper provides analysis of time-varying stripline loads and the impact of these loads on system performance. Further, an approach to reduce dielectric stress levels through active damping is presented as a means to increase system reliability and lifetime.

Impact of Time-Varying Loads on the Programmable Pulsed Power Driver Called Genesis

The success of dynamic materials properties research at Sandia National Laboratories has led to research into ultralow impedance, compact pulsed power systems capable of multi-MA shaped current pulses with rise times ranging from 220 to 500 ns. The Genesis design consists of two hundred and forty 200 kV, 80 kA modules connected in parallel to a solid dielectric disk transmission line and is capable of producing 280 kbar of magnetic pressure (>; 500 kbar pressure in high Z materials) in a 1.75 nH, 20-mm wide stripline load. Stripline loads operating under these conditions expand during the experiment resulting in a time-varying load that can impact the performance and lifetime of the system. This paper provides analysis of time-varying stripline loads and the impact of these loads on system performance. Further, an approach to reduce dielectric stress levels through active damping is presented as a means to increase system reliability and lifetime.

Large area dielectric breakdown under pulsed conditions

Summary form only given. Dielectric materials are a critical component of pulsed power systems. Often times these materials are the limiting factor in system design and operation. To aid in the understanding and prediction of the breakdown of polypropylene under pulsed operating conditions experimental evaluation and analysis of large area (48 × 20 in.) sheets of 1/16 in. polypropylene material between aluminum plates were explored. Accelerated lifetime tests in the thousands of shots range were made with various types of coating on the aluminum electrodes and with bare electrodes. The aluminum and polypropylene were assembled under vacuum and sealed along the plate edges. Testing was conducted utilizing pulses with two different damped ringing shapes. This paper describes the testing configuration and process, followed by a discussion of the breakdown data and how it relates to historical test results.

A novel electron gun with an independently addressable cathode array

The design of a novel electron gun with an array of independently addressable cathode elements is presented. Issues relating to operation in a 6.5 Tesla axial magnetic field are discussed. Simulations with the TriComp electromagnetic field code that were used to determine the space charge limited tube characteristic and to model focusing of the electron beam in the magnetic field are reviewed. Foil heating and stress calculations are discussed. The results of CYLTRAN simulations yielding the energy spectrum of the electron beam and the current transmitted through the foil window are presented.

Electron beam applications at Sandia national Laboratories 1.5 MW HAWK facility

The need for ground based missile-scale and air-breathing propulsion test capabilities above Mach 7 led to the reconstruction of the HAWK electron beam accelerator approximately a decade ago. Electron beams were chosen as a source for adding thermal energy to supersonic gas flows to achieve representative temperatures and dynamic gas pressures along the desired flight corridor. Since the first incarnation of HAWK, investigations utilizing the system have spanned electron beam pumped lasers to beam transport development for radiation generation or energy deposition. Early experiments were limited to the use of foil and plasma windows as enablers for beam extraction thereby limiting achievable beam currents and durations. This was followed by modifications to the HAWK system in 2004 accommodating windowless beam extraction with an axial magnetic field. This integrated hardware addition was demonstrated at a beam current of 1.5 A for 5ms durations. Recent experiments have added the new capability of coupling the electron beam into a Magnetohydrodynamic chamber. This paper discusses the HAWK accelerator and the achievements that it has enabled.

A testbed for high voltage, high bandwidth characterization of nonlinear dielectrics

The dielectric response of many high permittivity materials is nonlinear with both field and frequency. For example, ferroelectric materials exhibit a hysteretic polarization - electric field (P-E) response similar to the B-H curve of ferromagnetic materials. These P-E hysteresis loops are typically measured at low frequencies; the material behavior at high frequencies is less understood. To address this information gap, a test bed has been created to characterize non-linear material behavior at high frequencies and high voltages. This paper will report testbed goals in addition to design, assembly, analysis, and issues. Preliminary results will also be presented from commercially available nonlinear capacitors and in-house fabricated ferroelectric materials, including 10 nF non-linear BaTiO3-based capacitors and 3 mm thick lead zirconate titanate (PZT)-based materials.